Aluminium-Based Alloy And Moulded Part Consisting Of Said Alloy

ABSTRACT

The invention relates to an aluminium-based alloy comprising the following weight percent of constituents: between approximately 15% and 30% silicon, at least 1% nickel, in addition to at least one of the two constituents iron or titanium, the sum of the fractions of nickel, iron and titanium totalling at least 3%. The invention also relates to a moulded part consisting of said alloy.

The invention relates to an aluminum-based alloy, at least comprising, in percent by weight, between approximately 15% and approximately 30% silicon and at least 1% nickel, and to a shaped part made from an alloy of this type.

Increasing demands are being imposed on the materials used in particular in the field of internal combustion engines for modern motor vehicles, wherein a low weight and high thermal and mechanical stresses are required. This follows inter alia from higher combustion pressures and combustion temperatures and a narrower web width between the cylinders. Spray-compacted light metal alloys which are already in use, such as for example AlSi25Cu4Mg, in particular in diesel applications no longer meet the current demands imposed on cylinder liners. Also other components, which are not cast in place but rather are produced by machining and/or by a hot-forming process no longer meet the increased demands in motor construction. These are in particular highly stressed parts such as pistons or connecting rods.

The object of the invention is to provide an aluminum-based alloy which has high mechanical characteristic values, in particular at high temperatures. Furthermore, the object of the invention is to provide a shaped part made from an alloy of this type.

For an alloy of the type described in the introduction, this object is achieved according to the invention by the features of claim 1.

The high nickel content of at least 1% combined with the fact that furthermore at least one of the two elements iron and titanium is present and that the sum of the nickel, iron and titanium contents amounts to at least 3% has the advantageous result that the alloy has sufficient quantities of aluminides, which are generally precipitated in finely distributed (dispersed) form and are present within the microstructure. These aluminides are distinguished by a high melting point and provide the alloy with a very good hot strength. Furthermore, the creep resistance of the alloy is increased on account of the low solubility of the aluminides.

The sum of the iron, nickel and titanium contents is advantageously no more than 9%. It is particularly advantageous for nickel to be present in a concentration of at least 2%, in which case the sum of the nickel, iron and titanium contents amounts to between 4% and 8%. The alloys according to the invention have particularly advantageous properties within these ranges of values.

Furthermore, it is advantageous for the silicon content to amount to between 20% and 28%, with the silicon content particularly advantageously amounting to between 23% and 27%. It is in this way possible to further optimize the alloy according to the invention in terms of its mechanical and thermal properties. Furthermore, it is advantageous for the alloy to have a magnesium content of between 0.1% and 1%. It is particularly advantageous for the magnesium content to amount to between 0.2% and 0.7%. By forming precipitations, for example Mg₂Si, the magnesium also increases the strength of the alloy. Further precipitations (e.g. Al₂CuMg) may occur in the presence of further elements, such as for example copper, resulting in further advantageous effects, such as for example a high hot strength and a good long-term stability at high temperatures.

It is also preferable for the alloy to have a copper content of between 0.5% and 6%, particularly advantageously between 0.5% and 2% and especially advantageously between 0.7% and 1.7%. An alternative particularly advantageous group of alloys in the presence of copper advantageously has a copper content of between 1% and 3.5%, particularly advantageously between 1% and 3%. In this case, the advantages of the presence of copper in the concentration ranges described result in particular in conjunction with the presence of magnesium, in which case it is advantageous for the ratio of the copper content to the magnesium content to be between 0 and 2. In an alternative preferred group of alloys according to the invention, the ratio of the copper content to the magnesium content is between 2 and 6. However, in the alloy according to the invention it is possible for there to be no copper present, making the alloy particularly suitable for applications which require a high solidus temperature.

Furthermore, it is advantageous for the alloy according to the invention to have an iron content of between 0% and 5%. The iron content is particularly advantageously between 0% and 4%.

Furthermore, cobalt may preferably be present in an alloy according to the invention, in an amount of between 0% and 1.8%, particularly preferably between 0% and 1.25%. Depending on the precise optimization of the alloy according to the invention, the nickel which is always present may be at least partially replaced by the elements iron and/or cobalt.

Furthermore, advantageous properties of the alloy according to the invention may ensue if the alloy has a titanium content of between 0.05% and 0.7%, preferably between 0.1% and 0.5% and particularly preferably between 0.1% and 0.4%. Zirconium may likewise advantageously be present at a level of between 0% and 0.7%, particularly advantageously between 0.1% and 0.5%. On account of the way in which titanium and zirconium have a reciprocal influence on one another in the alloy, it may be particularly advantageous for the sum of the zirconium content and the titanium content in total to be between 0.1% and 0.5%.

Further advantageous properties of the alloy result if said alloy has a chromium content of between 0% and 1 %, preferably between 0% and 0.8% and particularly preferably between 0% and 0.5%. In general, the elements chromium, titanium and zirconium form precipitations mostly in the form of aluminides, which increase the recrystallization temperature and restrict the mobility of grain boundaries at elevated temperatures. This leads to an improved hot strength. These precipitations, for example CrAl₇, are likewise in the form of finely dispersed precipitations (dispersoids). Furthermore, the alloy according to the invention can advantageously be improved by the alloy having a manganese content of between 0% and 2.2%, preferably between 0% and 1.5% and particularly preferably between 0% and 0.8%. Manganese and also cobalt advantageously improve the hot strength of the alloy and influence the solidification morphology of Al₃Fe in the direction of the globulitic form. In general, manganese and cobalt aluminides (Al₆Mn and Co₂Al₉, respectively) are likewise present in dispersoid-precipitated form.

An alloy according to the invention which is particularly preferred in terms of its properties consists of 25% silicon, 2.5% iron, 2.5% copper, 0.5% magnesium, 0.15% titanium, 2.5% nickel, 0.3% cobalt, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 2.5% copper, 0.5% magnesium, 0.15% titanium, 7% nickel, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 4% iron, 1.5% copper, 0.5% manganese, 0.5% magnesium, 0.3% chromium, 0.25% titanium, 3% nickel, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 2.5% iron, 5% copper, 0.5% titanium, 2% nickel, 0.5% cobalt, 0.4% zirconium, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 1.5% iron, 5% copper, 0.3% chromium, 0.25% titanium 2% nickel, 0.3% cobalt, 0.4% zirconium, 0.4% antimony, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 4% iron, 0.5% magnesium, 0.3% chromium, 0.15% titanium, 3% nickel, 0.2% zirconium, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 3.5% iron, 1% copper, 0.5% magnesium, 0.3% chromium, 0.15% titanium, 3% nickel, 0.5% cobalt, 0.2% zirconium, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 3.5% iron, 1% copper, 0.5% manganese, 0.5% magnesium, 0.3% chromium, 0.15% titanium, 3% nickel, 0.2% zirconium, remainder aluminum apart from inevitable impurities.

A further particularly preferred alloy consists of 25% silicon, 3.5% iron, 1% copper, 0.5% manganese, 0.3% chromium, 0.15% titanium, 3% nickel, 0.2% zirconium, remainder aluminum apart from inevitable impurities.

The abovementioned alloys according to the invention preferably include further constituents at most at the level of fundamentally unavoidable impurities caused by the technological processes employed. The impurities may also be present in higher concentrations to the extent that the impurity in each case has no significant effects on the materials properties.

The alloy according to the invention is particularly preferably characterized by being produced with a high cooling rate. The alloy may particularly preferably be produced by means of spray-compacting, in which spray-compacting method a particularly high cooling rate is generally present. Alternatively, however, it is also possible to use conventional powder metallurgy processes or also casting processes. The high solidification rate of the alloy on account of the high cooling rate favors the precipitation of the alumides in a globulitic form rather than an acicular form as would be the case at slow solidification rates.

This makes a strength-enhancing contribution to the alloys without causing them to suffer embrittlement.

The object of the invention relating to a shaped part is achieved by virtue of the fact that the shaped part at least partially consists of the alloy as claimed in one of claims 1 to 43. The shaped part may also be a part which only partially consists of an alloy according to the invention, which for example is then surrounded by a further material by casting in a further processing step. In particular, the shaped part may be a cylinder block of a motor vehicle, in which cylinder liners consist of an alloy according to the invention and are surrounded by casting with a further alloy. In this case, the shaped part may particularly advantageously be produced by means of spray-compacting and if appropriate further process steps.

Further advantages and features of an alloy according to the invention and of a shaped part according to the invention will emerge from the exemplary embodiments outlined below and the dependent claims.

Nine particularly preferred exemplary embodiments of an alloy according to the invention are described in more detail below.

The quantitative contents of the various metallic components of the alloys L1 to L9 according to the invention will emerge from the following table, in which the details of the contents are in each case given in percent by weight: Si Fe Cu Mn Mg Cr Ti Ni Co Zr Sb L1 25 2.5 2.5 0.5 0.15 2.5 0.3 L2 25 2.5 0.5 0.15 7 L3 25 4 1.5 0.5 0.5 0.3 0.25 3 L4 25 2.5 5 0.5 2 0.5 0.4 L5 25 1.5 5 0.3 0.25 2 0.3 0.4 0.4 L6 25 4 0.5 0.3 0.15 3 0.2 L7 25 3.5 1 0.5 0.3 0.15 3 0.5 0.2 L8 25 3.5 1 0.5 0.5 0.3 0.15 3 0.2 L9 25 3.5 1 0.5 0.3 0.15 3 0.2

The respective concentrations are in each case to be complied with to a respective relative accuracy of approximately 10%, preferably less than 5%.

These nine particularly preferred alloys in tests gave the mechanical and thermal properties described below and enumerated in table form (static strength, dynamic strength, modulus of elasticity and solidus temperature). The material AlSi25Cu4Mg, which is known as an alloy for liners of cylinders and is also known under the trade name DISPAL®S260 is also included in the list, for reasons of comparison.

1) Static Strength: As pressed, T6 As pressed, T6 tested at RT tested at RT tested at 200° C. tested at 200° C. Rp0.2 Rm A5 Rp0.2 Rm A5 Rp0.2 Rm A5 Rp0.2 Rm A5 (MPa) (MPa) (%) (MPa) (Mpa) (%) (MPa) (MPa) (%) (MPa) (MPa) (%) S260 199 285 1.5 261 314 0.8 157 214 3.2 203 227 2.1 L1 218 367 1.6 200 280 2.65 L2 188 316 1.4 479 487 0.23 187 255 1.63 235 255 2.6 L3 259 388 1.09 492 503 0.23 L4 216 352 1.2 400 430 0.34 188 256 1.9 185 256 2.1 L5 199 334 1.92 414 498 0.73 146 192 7.98 180 240 2.48 L6 206 321 1.03 233 326 0.76 200 237 2.3 L7 250 392 0.85 298 399 0.61 211 293 2.02 224 297 1.16 L8 256 397 1.17 296 397 0.84 225 308 1.9 220 293 1.52 L9 251 388 1.32 230 368 1.21 193 256 4.36 189 255 2.2

The state indicator “as pressed” relates to a material which has been subjected to a standard extrusion process. The state indicator “T6”, as per convention (for example DIN EN 515) corresponds to “solution-annealed and artifically aged up to maximum strength”. The meanings of the materials properties measured, as per standard convention (for example DIN EN 10002-1) are as follows:

-   -   R_(p0.2): Elongation limit at non-proportional elongation, 0.2%         proof stress.     -   Rm: Tensile strength (from tensile test).     -   A₅: Elongation at break, total residual elongation occurring at         break when using short proportional tensile test specimens.

2) Dynamic Strength Axial test, R = 0.1 Test temperature 200° C. Stress amplitude at 5* 10-6 load changes, State 10% survival probability (MPa) S260 T6 33.8 L1 As pressed 63.9 L2 T6 71.1 L6 T6 51.4 L7 T6 68.2 L8 T6 68.7

In the present instance, not all of the nine example alloys were subjected to the dynamic strength test.

3) Modulus of Elasticity Modulus of elasticity at Modulus of elasticity Alloy RT (GPa) at 200° C. (GPa) S260 89 83 L1 102 95 L2 104 98 L3 113 — L4 108 89 L5 105 72 L6 102 96 L7 105 99 L8 105 99 L9 102 99

In the above, the values for L3, L4, L5 and L9 are taken from the tensile test, while the other values are derived from resonant excitation.

4) Solidus Temperature Solidus temperature Alloy (degree Celsius) S260 505 L1 532 L2 534 L3 535 L4 533 L5 531 L6 549 L7 532 L8 533 L9 532

It can be seen that it was possible for in particular the solidus temperature to be shifted significantly upward compared, for example, to alloy S260. Alloy L6, which is the only one that does not contain any copper, has a particularly high solidus temperature and can preferably be used for corresponding requirements.

Moreover, casting tests have shown that all of the alloys had improved distortion properties compared to S260. None of the alloys were subject to the cast-in parts buckling or melting through. It was possible to effectively reduce the extent of disadvantageous coarsening of the Si particles caused by the temperature rise which takes place during casting and/or a subsequent heat treatment.

Casting tests carried out on the preferred example alloys were carried out with the objective of using the alloys for cast-in cylinder liners of internal combustion engines. However, other uses, in particular in the field of internal combustion engines, for example for connecting rods, pistons or cylinder heads, are also advantageous on account of the good thermal and mechanical properties. 

1-47. (canceled)
 48. An aluminum-based alloy, at least comprising, in percent by weight: between 22.5% and 27.5% silicon, between 1.8% and 3.3% nickel and between 2.25% and 4.4% iron, wherein the sum of the nickel, iron and cobald contents amounts to between 4.8% and 7.7%, between 0.4% and 0.6% magnesium, wherein the sum of the copper and magnesium contents amounts to between 0.4% and 3.3%, and between 0.1% and 0.19% titanium, wherein the sum of the chromium, titanium and zirconium contents amounts to between 0.1% and 1.2%.
 49. The alloy as claimed in claim 48, wherein the alloy has a copper content of between 0.5% and 2.9%.
 50. The alloy as claimed in claim 48, wherein the alloy has a copper content of between 0.7% and 1.7%.
 51. The alloy as claimed in claim 48, wherein the ratio of the copper content to the magnesium content is between 2 and
 5. 52. The alloy as claimed in claim 48, wherein the amount of the copper content is larger than the amount of the magnesium content.
 53. The alloy as claimed in claim 48, wherein the ratio of the iron content to the copper content is between 1 and 3.5.
 54. The alloy as claimed in claim 48, wherein the ratio of the iron content to the nickel content is between 1 and 1.5.
 55. The alloy as claimed in claim 48, wherein the alloy has a cobalt content of between 0% and 1.25%.
 56. The alloy as claimed in claim 48, wherein the cobalt content amounts to between 0.27% and 0.55%.
 57. The alloy as claimed in claim 48, wherein the alloy has a zirconium content of between 0% and 0.7%.
 58. The alloy as claimed in claim 48, wherein the alloy has a zirconium content of between 0.18% and 0.22%.
 59. The alloy as claimed in claim 48, wherein the alloy has a chromium content of between 0% and 0.33%.
 60. The alloy as claimed in claim 48, wherein the alloy has a manganese content of between 0% and 0.8%.
 61. The alloy as claimed in claim 48, wherein the manganese content amounts to between 0.45% and 0.55%.
 62. The alloy as claimed in claim 48, to a relative accuracy of 10% consisting of: Silicon: 25%; Iron: 2.5%; Copper: 2.5%; Magnesium: 0.5%; Titanium: 0.15%; Nickel: 2.5%; Cobalt: 0.3%; remainder aluminum apart from impurities.
 63. The alloy as claimed in claim 48, to a relative accuracy of 10% consisting of: Silicon: 25%; Iron: 4%; Magnesium: 0.5%; Chromium: 0.3%; Titanium: 0.15%; Nickel: 3%; Zirconium: 0.2%; remainder aluminum apart from impurities.
 64. The alloy as claimed in claim 48, to a relative accuracy of 10% consisting of: Silicon: 25%; Iron: 3.5%; Copper: 1%; Magnesium: 0.5%; Chromium: 0.3%; Titanium: 0.15%; Nickel: 3%; Cobalt: 0.5%; Zirconium: 0.2%; remainder aluminum apart from impurities.
 65. The alloy as claimed in claim 48, to a relative accuracy of 10% consisting of: Silicon: 25%; Iron: 3.5%; Copper: 1%; Manganese: 0.5%; Magnesium: 0.5%; Chromium: 0.3%; Titanium: 0.15%; Nickel: 3%; Zirconium: 0.2%; remainder aluminum apart from impurities.
 66. The alloy as claimed in claim 48, wherein further constituents are present at most as impurities.
 67. The alloy as claimed in claim 48, the alloy being produced in conjunction with a high cooling rate.
 68. A spray-compacted aluminum-based alloy, at least comprising, in percent by weight: between 22.5% and 27.5% silicon, between 1.8% and 3.3% nickel and between 2.25% and 4.4% iron, wherein the sum of the nickel, iron and cobald contents amounts to between 4.8% and 7.7%, between 0.4% and 0.6% magnesium, wherein the sum of the copper and magnesium contents amounts to between 0.4% and 3.3%, and between 0.1% and 0.19% titanium, wherein the sum of the chromium, titanium and zirconium contents amounts to between 0.1% and 1.2%.
 69. The alloy as claimed in claim 68, wherein the silicon content amounts to between 24% and 26%.
 70. The alloy as claimed in claim 68, the alloy being produced in conjunction with a high cooling rate.
 71. A shaped part, made from a spray compacted, aluminum-based alloy, said alloy at least comprising, in percent by weight: between 22.5% and 27.5% silicon, between 1.8% and 3.3% nickel and between 2.25% and 4.4% iron, wherein the sum of the nickel, iron and cobald contents amounts to between 4.8% and 7.7%, between 0.4% and 0.6% magnesium, wherein the sum of the copper and magnesium contents amounts to between 0.4% and 3.3%, and between 0.1% and 0.19% titanium, wherein the sum of the chromium, titanium and zirconium contents amounts to between 0.1% and 1.2%.
 72. The shaped part as claimed in claim 71, the shaped part being produced by means of spray-compacting and if appropriate further process steps.
 73. The shaped part as claimed in claim 71, wherein the shaped part comprises a cylinder liner for an internal combustion engine.
 74. The shaped part as claimed in claim 71, wherein the shaped part comprises a piston for an internal combustion engine. 